(1) Field of the Invention
The present invention relates to an electrode for a switch and a vacuum switch, and a method of manufacturing the electrode for the switch or the vacuum switch.
(2) Description of Related Art
Since the vacuum switch employs a vacuum insulation having a high insulation performance, and does not use a gas such as SF6 or the like having a high global warming coefficient, it is a switch which can achieve both downsizing and reduction of an environmental load.
The vacuum switch carries out an electric current break or the like in an inner portion of a vacuum vessel, however, a method of manufacturing the vacuum vessel in a high vacuum exists as a method of manufacturing the vacuum vessel. In this case, in a brazing in a manufacturing step of the vacuum vessel, it is necessary to properly use a brazing filler metal in correspondence to a material between members constructing the vacuum vessel. Accordingly, it is necessary to separate the brazing into at least two steps.
A first step is a step of connecting metals to each other such as a connection between an electrode and a conducting bar, and a second step is a step of including the members adhered in accordance with the first step in an inner portion, connecting an insulation tube and a metal end plate, and constructing a vacuum sealed vacuum vessel. The first step is structured such as to connect the metals to each other, however, the second step has to connect the insulation material and the metal. Accordingly, it is necessary to use different brazing filler materials, respectively.
Therefore, there is a possibility that the brazing filler material used in the first step is again molten in the second step, and if the brazing filler material is molten in the second step, the brazing filler material used for connecting the electrode and the conducting rod in the first step is deformed, so that there is a possibility that an air gap is generated between the electrode and the conductor rod, and a displacement is generated between the electrode and the conducting rod.
In order to prevent the displacement between the electrode and the conducting rod as mentioned above from being generated, for example, there is a structure described in patent document 1 (JP-A-5-298971). The patent document 1 has a description of an electrode which has an electrode rod provided with protruding portions 6a and 7a in an end portion, and an insertion hole having the same shape as the end portion of the electrode rod, and in which grooves 4a and 5b are formed in an inner portion, and describes an assembling method of the electrode rod and the electrode for finishing an assembly by setting a brazing filler material to a joint position between the electrode rod and the electrode, inserting the electrode rod to an electrode rod insertion port of the electrode, and rotating at about 90 degree in such a manner as to guide the protruding portions 6a and 7a of the end portion of the electrode rod to a groove in an inner portion of the electrode and locking, as an assembling method of the electrode rod and the electrode (paragraph [0008] to [0009] of the specification of the patent document 1.) Further, there is described that an object of the invention is to provide a vacuum valve which can prevent the electrode from coming off and being inclined and prevent a positional displacement between the electrode rod and the electrode in a final assembling step, and has a high reliability without lowering a performance serving as the vacuum valve, in the case that a brazing temperature in a partial assembling step is the same as a brazing temperature at which a vacuum sealing is carried out in a final assembling step (paragraph [0005] of the specification of the patent document 1).
In this case, in the case that an air gap is generated between the electrode and the conducting rod, the air gap portion is occupied with an insulation medium such as a vacuum or the like. Since this portion exhibits a high insulating property, this portion comes to a high resistance portion at a time of conducting an electric current, and a conducting property of the electric current is lowered. Further, since a coefficient of thermal conductivity is lower in the air gap portion (for example, filled with a vapor or a gas in the case of an air brake insulation switch, filled with a gas in the case of a gas insulation switch, and filled with a vacuum in the case of a vacuum insulation switch, respectively) in comparison with the electrode corresponding to the metal material, and a heat conduction is prevented in the air gap portion, the electrode coming to a high temperature at a time when the electric current is broken is hard to be radiated heat, and a possibility that the electrode member is molten becomes higher. There is a risk that they cause a reduction of a reliability.
In the patent document 1 mentioned above, the protruding portion of the end portion of the electrode rod is rotated and locked in such a manner as to be guided to the groove in the inner portion of the electrode, however, on the assumption that the assembling method mentioned above is achieved, it is necessary that a clearance gap is provided to some extent between the protruding portion of the end portion of the electrode rod and the groove in the inner portion of the electrode. In the case that no clearance gap is provided, the protruding portion of the end portion of the electrode rod can not be rotated with respect to the groove in the inner portion of the electrode. Further, the clearance gap corresponds to the air gap portion mentioned above eventually. Accordingly, in the case of intending to fix the electrode rod and the electrode on the basis of a rotation, it is unavoidable that an air gap portion exists to some extent or is enlarged.